U.S. patent application number 10/099321 was filed with the patent office on 2002-10-17 for capping method and capping apparatus.
Invention is credited to Kasai, Mitsuru, Takebe, Minoru, Yoshida, Kenichiro.
Application Number | 20020148205 10/099321 |
Document ID | / |
Family ID | 18965922 |
Filed Date | 2002-10-17 |
United States Patent
Application |
20020148205 |
Kind Code |
A1 |
Takebe, Minoru ; et
al. |
October 17, 2002 |
Capping method and capping apparatus
Abstract
A screw capper 1 includes a capping head 6 which grips a cap 5,
a servo motor 7 which rotates the capping head, a voltmeter 10
which measures the torque of the capping head, an encoder 11 which
detects the rotational angle of the capping head, and a control
device 8 which controls the servo motor. In the screw capper, when
whether rotational fastening is acceptable is to be determined
during the rotational fastening, the measured value of the encoder
is measured from a predetermined measurement starting point until a
rotational fastening completion point, and if the measured
rotational angle is in the range of an acceptable decision angle
which is set in advance, it is determined that the rotational
fastening has been acceptably performed, whereas if the measured
rotational angle is not in the range of the acceptable decision
angle, it is determined that the rotational fastening is
unacceptable. In the screw capper, defective rotational fastening
can be detected, and reductions in costs can be realized compared
to a case where a device for detecting such defective rotational
fastening is separately provided.
Inventors: |
Takebe, Minoru;
(Ishikawa-Ken, JP) ; Kasai, Mitsuru;
(Ishikawa-Ken, JP) ; Yoshida, Kenichiro;
(Ishikawa-Ken, JP) |
Correspondence
Address: |
FLYNN, THIEL, BOUTELL & TANIS, P.C.
2026 Rambling Road
Kalamazoo
MI
49008-1699
US
|
Family ID: |
18965922 |
Appl. No.: |
10/099321 |
Filed: |
March 15, 2002 |
Current U.S.
Class: |
53/490 ;
53/331.5 |
Current CPC
Class: |
B67B 3/2093 20130101;
B67B 3/20 20130101; B67B 3/26 20130101 |
Class at
Publication: |
53/490 ;
53/331.5 |
International
Class: |
B65B 007/28 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2001 |
JP |
114945/2001 |
Claims
What is claimed is:
1. A capping method which uses a capping head which retains a cap,
and a motor which rotates the capping head, the capping method
causing the cap retained by the capping head to rotate in a
cap-closing direction and rotationally fastening the cap to a
container with a predetermined cap-closing torque, characterized in
that the capping method comprising the steps of: measuring a
rotational angle of the capping head from a predetermined
measurement starting point until a completion of rotational
fastening; and determining whether the rotational fastening is
acceptable, according to whether the rotational angle is within a
range of an acceptance decision angle which is set in advance.
2. A capping method according to claim 1, wherein the measurement
starting point is an engagement starting position at which when a
screw thread portion of the cap and a screw thread portion of the
container are rotated relatively to each other, leading ends of
both screw thread portions come into contact with each other.
3. A capping method according to claim 1, wherein the measurement
starting point is a point of transfer from temporary fastening for
rotationally fastening the cap with a low torque to final fastening
for rotationally fastening the cap with a higher torque than the
temporary fastening does.
4. A capping method according to claim 1, further comprising: a
step of effecting temporary fastening for rotationally fastening
the cap with a low torque; and a step of effecting final fastening
for rotationally fastening the cap with a higher torque than the
temporary fastening does, the measurement starting point being a
time point at which a rotational speed becomes lower than a
predetermined value during the temporary fastening.
5. A capper comprising a capping head which grips a cap, a motor
which rotates the capping head, a control device which controls the
motor to rotate the cap in a cap-closing direction and rotationally
fasten the cap to a container with a predetermined cap-closing
torque, characterized in that the capper provides rotational angle
detecting means for measuring a rotational angle of the capping
head, a value measured by the rotational angle detecting means
being inputted to the control device, and the control device
finding the rotational angle by measuring the value measured by the
rotational angle detecting means, from a predetermined measurement
starting point until a completion of rotational fastening, and
determining whether the rotational fastening is acceptable,
according to whether the rotational angle is within a range of an
acceptance decision angle which is set in advance.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a capping method of and a
capper for screwing a cap to a container.
DESCRIPTION OF THE PRIOR ART
[0002] A capper has heretofore been known which includes a capping
head which retains a cap, driving means which rotates this capping
head in forward and reverse directions, torque measuring means
which measures fastening torque which acts on the cap, and a
control device which controls the driving means. The capper
monitors the measured value of the torque and completes screwing
when the measured value reaches a predetermined rotational
fastening torque value. After the screwing has been completed, the
capper unfastens the cap to determine a cap-opening toque value,
and corrects a fastening torque value to be outputted to the
driving means, on the basis of the cap-opening torque value
(Japanese Patent Laid-Open No. 229593/1993).
[0003] In Japanese Patent Laid-Open No. 229593/1993, the
cap-opening torque value is compared with an acceptance decision
torque value which is set in advance, and when the difference
between these values exceeds an allowable range, a fastening torque
value to be transmitted to the driving means is corrected so that
the fastening torque value is managed with high precision.
[0004] In the case where the screw thread portion of a cap or the
screw thread portion of a container is defectively formed, for
example, the screw thread portion is damaged, packing inside the
cap may fail to come into abutment with the mouth portion of the
container, so that a predetermined fastening completion torque
value may be obtained. However, the art of the above-cited
specification has the problem of being unable to detect a case
corresponding to such defective rotational fastening.
[0005] As a method of solving such problem, it can be considered to
adopt a construction in which a detecting device for detecting
defective rotational fastening is separately provided on the
downstream of the capper. This construction, however, incurs an
increase in cost.
SUMMARY OF THE INVENTION
[0006] In view of the above-described problems, the first invention
provides a capping method which uses a capping head which retains a
cap, and a motor which rotates the capping head, the capping method
causing the cap retained by the capping head to rotate in a
cap-closing direction and screwing the cap to a container with a
predetermined cap-closing torque. The capping method includes the
steps of measuring a rotational angle of the capping head from a
predetermined measurement starting point until a completion of
rotational fastening, and determining whether the rotational
fastening is acceptable, according to whether the rotational angle
is within a range of an acceptance decision angle which is set in
advance.
[0007] The second invention provides a capper which includes a
capping head which grips a cap, a motor which rotates the capping
head, a control device which controls the motor to rotate the cap
in a cap-closing direction and rotationally fasten the cap to a
container with a predetermined cap-closing torque. In accordance
with the invention, the capper provides rotational angle detecting
means for measuring a rotational angle of the capping head. The
value measured by the rotational angle detecting means is inputted
to the control device, and the control device finds the rotational
angle by measuring the value measured by the rotational angle
detecting means, from a predetermined measurement starting point
until a completion of rotational fastening, and determines whether
the rotational fastening is acceptable, according to whether the
rotational angle is within a range of an acceptance decision angle
which is set in advance.
[0008] According to the invention, if the cap fails to be
rotationally fastened so that its packing comes into abutment with
the mouth portion of a container, owing to the defective formation
of a screw thread portion of the cap or the defective formation of
a screw thread portion of the container, that failure can be
measured as a decrease in the rotational angle of the cap.
[0009] Accordingly, by determining whether an angle by which the
cap actually rotates is within the range of the acceptable angle, a
decision as to whether rotational fastening is acceptable can be
accurately made in the capper. In addition, since the rotational
angle detecting means is merely provided in the capper, costs can
be reduced compared to a case where a device for detecting
defective rotational fastening is separately provided.
[0010] Further objects, features and advantages of the invention
will become apparent from the following detailed description of an
embodiment of the invention with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic plan view showing an embodiment of the
invention;
[0012] FIG. 2 is a diagram showing control of a control device
8;
[0013] FIG. 3 is a view showing a state in which to detect an
engagement starting point at which to start engagement between a
screw thread portion 5a of a cap 5 and a screw thread portion 2a of
a container 2;
[0014] FIG. 4 is a view showing the relationship between the
lifting and movement of a capping head 6; and
[0015] FIG. 5 is a view showing the relationship between the
detected torque value of a voltmeter 10 and the rotational angle
(rotational speed) of an encoder 11.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0016] The invention will be described below with reference to its
embodiment shown in the accompanying drawings. In FIG. 1, reference
numeral 1 denotes a rotary type of screw capper to which the
invention is applied.
[0017] The rotary type screw capper 1 includes carriages 3 (one of
which is shown) which are respectively provided at
circumferentially equally spaced positions around a rotator (not
shown) and on each of which a container 2 is to be placed, grippers
4 (one of which is shown) each of which grips the body portion of
the container 2 mounted on the carriages 3, capping heads 6 (one of
which is shown) each of which is provided at a position over the
carriage 3 to rotationally fasten a cap 5 to the mouth portion of
the container 2 gripped by the gripper 4, and a well-known type of
lifting cam (not shown) which serves as lifting means for lifting
the capping head 6. These capping heads 6 are respectively liftably
connected to servo motors 7 via spline shafts 9, and are capable of
being rotated in a horizontal plane.
[0018] The operation of these servo motors 7 is controlled by a
control device 8 which exercises general control over the entire
screw capper 1. When torque commands and speed commands are
transferred from the control device 8 to the servo motors 7, the
servo motors 7 are rotationally driven by the torque commands and
the speed commands to rotate the respective capping heads 6.
[0019] The above-described construction does not differ from that
of the rotary screw capper of the type which has heretofore been
known.
[0020] In the present embodiment, each of the servo motors 7 is
provided with a voltmeter 10 which serves as torque detecting means
for detecting its voltage and an encoder 11 which serves as
rotational angle detecting means for detecting pulses, and the
voltage signal of the voltmeter 10 and the pulse signal of the
encoder 11 are inputted to the control device 8 and, on the basis
of measured torque T and a rotational angle A obtained during the
rotational fastening of the cap 5, the control device 8 makes a
decision as to whether the rotational fastening is acceptable, a
detection of a defectively formed cap and a defectively formed
container, or a detection of a cap having no packing. The control
device 8 includes a calculating part 20 which computes the torque T
from the input voltage signal and the rotational angle A from the
input pulse signal, and a decision part 22 which makes a decision
as to whether the rotational fastening is acceptable, by comparing
the torque T and the rotational angle A inputted from the
calculating part 20 with an acceptance decision torque value and an
acceptance decision angle stored in a storage part 21,
respectively.
[0021] The decision as to whether the rotational fastening is
acceptable and the detection of a defectively formed cap and a
defectively formed container or a cap having no packing will be
described in detail with reference to the diagram shown in FIG.
2.
[0022] When the control device 8 recognizes that the capping head 6
has reached a predetermined rotational fastening starting position,
on the basis of a signal from a rotary encoder which measures the
rotational position of the rotator, the control device 8 first
outputs a command based on engagement control to the servo motor
7.
[0023] In this engagement control, during the start of engagement
of the cap 5 with the container 2, even if the cap 5 is brought
into anomalous engagement in an inclined state which is called
"cooked cap", the control device 8 drives the servo motor 7 with a
high torque command TQA so that the cap 5 can be forcedly brought
into engagement with the container 2, and also drives the servo
motor 7 with a high speed command SP(1) so that the time period of
rotational fastening can be reduced. Subsequently, this engagement
control is continued until the cap 5 makes one rotation (360
degrees), because the positional relationship between a leading end
of the screw thread portion of the container 2 and a leading end of
the screw thread portion of the cap 5 is not uniform.
[0024] Incidentally, this engagement control is not necessarily
needed, and may also be omitted as the case may be.
[0025] Then, while the capping head 6 is making one rotation, the
screw thread portion of the cap 5 comes into engagement with the
screw thread portion of the container 2, and when the control
device 8 recognizes that the capping head 6 has made one rotation,
on the basis of the number of pulses of the encoder 11 or the
elapse of time, the control device 8 proceeds from the engagement
control to temporary fastening control. In this temporary fastening
control, the control device 8 drives the servo motor 7 with a low
torque command TQB which indicates a smaller torque than does the
high torque command TQA for the engagement control, but continues
to drive the servo motor 7 with the high speed command SP(1).
During this time, the capping head 6 is made to rotate in a state
substantially close to an idle state until the cap 5 is rotated by
the required number of times, so that the torque of the capping
head 6 is maintained in an approximately zero state during this
time.
[0026] Then, when the capping head 6 is rotated by the required
number of times and packing (not shown) inside the cap 5 comes into
abutment with the upper end face of the mouth portion of the
container 2 and is brought into a compressed state, the resistance
applied from the container 2 increases and the rotational speed of
the capping head 6 decreases.
[0027] In other words, in the embodiment, by setting the torque
value of the above-described torque command TQB to a small value,
the rotational speed of the capping head 6 decreases with an
increase in the resistance applied from the container 2.
[0028] Then, when the rotational speed of the capping head 6
becomes lower than a temporary fastening completion speed F(1)
which is set in advance, the control device 8 recognizes that the
cap 5 has reached a temporary fastening completion state. When the
capping head 6 becomes lower than the temporary fastening
completion speed F(1) in this manner, the control device 8 sets
this point of time as a measurement starting point T(1) and starts
to measure the rotational angle A of the capping head 6 on the
basis of the pulse signals of the encoder 11, and in the meantime
outputs a command based on final fastening control. In this final
fastening control, the control device 8 drives the servo motor 7
with an intermediate torque command TQC which indicates a larger
torque than does the low torque command TQB and a smaller torque
than does the high torque command TQA, and also drives the servo
motor 7 with a low speed command SP(2) which indicates a lower
rotational speed than does the high speed command SP(1).
[0029] As the capping head 6 is made to rotate by the required
number of times in this manner and the compressive deformation of
the packing inside the cap 5 proceeds to increase the resistance
applied from the container 2, the rotational speed of the capping
head 6 gradually decreases and becomes lower than a final fastening
completion speed F(2). The control device 8 sets this point of time
as a measurement completion point T(2) and completes the
measurement of the rotational angle A. Then, after this measurement
completion point T(2), the control device 8 further drives the
servo motor 7 with the intermediate torque command TQC and the low
speed command SP(2) for only a predetermined time period B which is
set in advance, and completes the final fastening.
[0030] Incidentally, the time point of the completion of rotational
fastening is not limited to the time at which the rotation of the
capping head 6 actually comes to a stop and rotational fastening is
completed, and may also be a time point such as the time point T(2)
at which it can be determined that the rotational speed of the
capping head 6 has become lower than a predetermined rotational
speed and rotational fastening has been substantially completed, or
a time point T(3) at which rotational fastening is actually
completed and the capping head 6 comes to a stop.
[0031] Then, the control device 8 which has measured the rotational
angle A compares the rotational angle A with an acceptance decision
angle which is obtained by experiment or the like and stored in the
storage part 21 in advance, by means of the decision part 22, and
if the rotational angle A is within the range of the acceptance
decision angle, the control device 8 determines that optimum
rotational fastening has been performed. On the other hand, if the
rotational angle A is smaller than the acceptance decision angle,
the control device 8 determines that defective rotational fastening
due to a defectively formed cap or a defectively formed container
has occurred, whereas if the rotational angle A is larger than the
acceptance decision angle, the control device 8 determines that
defective rotational fastening due to a cap having no packing has
occurred.
[0032] Incidentally, if it is determined that the cap 5 is
defectively rotationally fastened to the container 2, the container
2 is eliminated from a line by a rejecting device which is not
shown, or an alarm is issued to urge an operator to eliminate the
defective product.
[0033] As can be understood from the above description, in
accordance with the embodiment, defective rotational fastening can
be detected in the screw capper 1, and since whether rotational
fastening is acceptable is merely determined on the basis of the
pulse signal of the encoder 11, reductions in costs can be realized
compared to a case where a defective rotational fastening detecting
device is separately provided.
[0034] Incidentally, in the above-described embodiment, the time
point at which the rotational speed of the capping head 6 becomes
lower than the temporary fastening completion speed F(1) which is a
criterion for determining whether the process is to proceed to the
final fastening is set as the measurement starting point T(1), but
the measurement starting point T(1) is not limited to such time
point. For example, the time point at which the rotation of the
capping head 6 comes to a stop may be set as the measurement
starting point T(1), or the criterion speed for starting
measurement may be set to a speed higher than the temporary
fastening completion speed F(1) so that measurement is started
before the process proceeds to the final fastening control.
[0035] In addition, in the above-described embodiment, the
measurement starting point T(1) is set as the time at which the
process proceeds from the temporary fastening to the final
fastening, but an engagement starting position at which to start
engagement between the cap 5 and the container 2 may be detected to
set this engagement starting position as the measurement starting
point T(1). A method of detecting this engagement includes the
steps of detecting a position at which, as shown in FIG. 3, a
bottom end portion 5a' of a screw thread portion 5a of the cap 5
(the lower leading end of the screw thread portion 5a) comes into
contact with a top end portion 2a' of a screw thread portion 2a of
the container 2 (the upper leading end of the screw thread portion
2a), on the basis of a variation in the value of the output torque
of the servo motor 7 detected by the voltmeter 10 during the
rotation of the servo motor 7, and setting the detected position as
the engagement starting position. In the case where the engagement
starting position is to be detected, software need only be added to
the control device 8 and the construction of the screw capper 1 may
be unchanged.
[0036] Specifically, as shown on the left-hand side of FIG. 4, a
descending stop section D in which the capping head 6 stops
descending (the capping head 6 travels at the same height) is
formed on the cam surface of the lifting cam which lifts the
capping head 6. The descending stop section D is set to a section
which is halfway in the process of descending the capping head 6 to
a rotational fastening height and is between the moment when the
cap 5 is placed on the container 2 and the moment when the female
thread 5a of the cap 5 is urged against the male thread 2a of the
container 2 by a spring 14 resiliently fitted between the capping
head 6 and the spline shaft 9.
[0037] Incidentally, since the urging of the cap 5 by the capping
head 6 is started immediately before the lifting cam reaches its
lowermost point, FIG. 4 shows the starting point of a rotational
fastening section W before the lowermost point.
[0038] Then, when the capping head 6 is positioned in the
descending stop section D, the height of the cap 5 retained by the
capping head 6 is set so that the lowermost end of the bottom end
portion 5a' of the female thread 5a of the cap 5 and the uppermost
end of the top end portion 2a' of the male thread 2a of the
container 2 are vertically disposed at approximately the same
height that enables abutment between the lowermost end of the
bottom end portion 5a' and the uppermost end of the top end portion
2a' (at the height shown in FIG. 3). When the cap 5 is rotated at
this height, the bottom end portion 5a' of the female thread 5a and
the top end portion 2a' of the male thread 2a of the container 2
are necessarily brought into abutment with each other during the
process of rotation of the cap 5. During this time, a load which
works in the rotational direction occurs in the cap 5.
[0039] Then, in the present embodiment, when the capping head 6
stops descending in the descending stop section D, the control
device 8, while detecting through the voltmeter 10 torque which
acts on the cap 5, causes the servo motor 7 to make one rotation in
the reverse or forward direction, thereby causing the cap 5
retained by the capping head 6 to make one rotation in the reverse
or forward direction.
[0040] When the cap 5 is caused to make one rotation in this
manner, the bottom end portion 5a' of the female thread 5a of the
cap 5 and the top end portion 2a' of the male thread 2a of the
container 2 come into abutment with each other once during the
rotational process of the cap 5. At the time of this abutment, a
maximum output torque P (a load working in the rotational
direction) during the process of causing the cap 5 to make one
rotation is measured by the voltmeter 10, and when the measured
result is inputted to the control device 8, the control device 8
recognizes the rotational angular position of the servo motor 7 at
that time by the encoder 11. FIG. 5 shows the relationship between
the rotational angular position of the servo motor 7 (the
rotational angular position of the cap 5 and the capping head 6)
detected by the encoder 11 and the output torque detected by the
voltmeter 10 when the servo motor 7 is caused to make one rotation
in the direction in which the cap 5 is rotationally fastened. When
the bottom end portion 5a' of the female thread 5a of the cap 5 and
the top end portion 2a' of the male thread 2a of the container 2
come into abutment with each other, the output torque abruptly
increases as shown by a hill-like shape in FIG. 5. That is, this
position P becomes the engagement starting position.
[0041] Incidentally, the method of detecting the engagement
starting position is not limited to the above-described method of
detecting the engagement starting position on the basis of a
variation in the detected value of the output torque. For example,
as disclosed in Japanese Patent Publication No. 86034/1995, a
position at which when a cap is rotated in the reverse direction,
the engagement between the screw thread portions of both the cap
and a container is released and a position in which the cap falls
may be detected as the engagement starting position.
[0042] In addition, in the embodiment, torque during rotational
fastening is detected by using the voltmeter 10, but an ammeter or
a load cell may also be used. In addition, actually outputted
torque may of course also be directly detected. Furthermore,
rotational fastening may be effected by command torque and the
rotational speed of the capping head 6 without providing torque
detecting means such as the voltmeter 10.
[0043] Furthermore, although in the embodiment the invention is
applied to the rotary type screw capper 1, the invention is not
limited to this type of screw capper, and may also be applied to a
line type screw capper.
[0044] Although the embodiment of the invention has been
specifically described above, the invention is not limited to only
the embodiment and can of course be modified in various manners
without departing from the scope and spirit of the invention.
* * * * *